1. Field of the Invention
This invention relates to a formed article of fiber-reinforced thermoplastic resin excelling in wear resistance, and more particularly to a formed article of fiber-reinforced thermoplastic resin manufactured in the shape of a varying sliding member by subjecting to injection molding or extrusion molding a fiber-reinforced thermoplastic resin having the sliding quality thereof improved by incorporation therein of a suitable amount of a material possessing a storage elastic modulus within a prescribed range as a sliding property-imparting agent. The term xe2x80x9csliding property-imparting agentxe2x80x9d used herein means a substance which is capable of improving a sliding property of the formed article of thermoplastic resin or lowering a friction coefficient thereof.
2. Description of the Prior Art
Heretofore, it has been customary to use a resin excelling in heat resistance and mechanical strength for resinous products which are used in sliding members. Specifically, the idea purporting that the resin to be used ought to acquire improved wear resistance by the step of increasing the rigidity of the resin prevails. This increase of the rigidity of resin is generally attained by the method of incorporating reinforcing fibers in the resin. When the resin obtained by this method is used particularly for the sliding member in a slide fastener, however, the sliding member has only low durability because it exhibits such notably inferior wear resistance that in a reciprocating closing test performed in accordance with Japanese Industrial Standard (JIS) S 3015, it becomes inoperative after about 60 open-close reciprocations.
When the formed article of thermoplastic resin is found to be deficient in rigidity, the thermoplastic resin used therein is generally made to incorporate therein a suitable amount of reinforcing fibers by way of compensation for shortage of mechanical strength. In terms of wear resistance, however, the reality of the reinforced thermoplastic resin is that the reinforcing fibers cause the thermoplastic resin to lose wear resistance because they are fated to function conversely as an abrasive.
An object of the present invention is to provide a formed article of thermoplastic resin which, with the view of improving the wear resistance of such a fiber-reinforced thermoplastic resin as mentioned above notably degraded in consequence of the addition of reinforcing fibers, incorporates therein a suitable amount of a material possessing an appropriate storage elastic modulus in the standard range of service temperatures or operating temperatures as a sliding property-imparting agent and acquires the improvement of wear resistance and proves fit for use as a sliding member.
To accomplish the object mentioned above, the basic mode of the present invention resides in providing a formed article of thermoplastic resin, which is characterized by comprising a fiber-reinforced resin material of a thermoplastic resin containing reinforcing fibers and incorporating therein additionally as a sliding property-imparting agent a material having a storage elastic modulus in the range of 3.5xc3x97108 Pa to 5.0xc3x97108 Pa in a service temperature range of 30xc2x0 C. to 70xc2x0 C.
One specific mode of the present invention provides a formed article of thermoplastic resin, which is characterized by comprising a fiber-reinforced resin material of a polyamide-based resin containing reinforcing fibers and incorporating therein additionally as a sliding property-imparting agent a material having a storage elastic modulus in the range of 3.5xc3x97108 Pa to 5.0xc3x97108 Pa in a service temperature range of 30xc2x0 C. to 70xc2x0 C. at a ratio in the range of 4 to 10% by weight, based on the total weight of the resin and the reinforcing fibers mentioned above.
Another specific mode of the present invention provides a formed article of thermoplastic resin, which is characterized by comprising a fiber-reinforced resin material of a thermoplastic resin (excluding a polyamide-based resin) containing reinforcing fibers and incorporating therein additionally as a sliding property-imparting agent a material having a storage elastic modulus in the range of 3.5xc3x97108 Pa to 5.0xc3x97108 Pa in a service temperature range of 30xc2x0C. to 70xc2x0 C. at a ratio in the range of 4 to 20% by weight, based on the total weight of the resin and the reinforcing fibers mentioned above.
Other objects, features, and advantages of the invention will become apparent from the following description taken together with the drawings, in which:
FIG. 1 is a graph showing changes in amount of abrasion found in an abrasion resistance test performed on polybutylene terephthalate containing 30% by weight of glass fibers and a fiber-reinforced resin containing the glass fiber-containing polymer just mentioned and 10% by weight of polytetrafluoroethylene additionally incorporated therein;
FIG. 2 is a graph showing changes in the storage elastic modulus of polytetrafluoroethylene and that of polybutylene terephthalate containing 30% by weight of glass fibers with temperature;
FIG. 3 is a graph showing changes in the storage elastic modulus of polyethylene and that of polybutylene terephthalate containing 30% by weight of glass fibers with temperature;
FIG. 4 is a graph showing changes in the amount of abrasion found in an abrasion resistance test performed on a polyamide-based resin containing 50% by weight of glass fibers and species of this fiber-reinforced resin just mentioned additionally incorporating therein 5% by weight, 10% by weight, and 20% by weight respectively of polyethylene;
FIG. 5 is a graph showing the range of storage elastic modulus of a material usable as a sliding property-imparting agent in the present invention;
FIG. 6 is a graph showing the results of an abrasion resistance test performed on test pieces prepared from a polyamide-based resin containing 50% by weight of glass fibers and species of this fiber-reinforced resin just mentioned additionally incorporating herein 2.5% by weight, 5% by weight, 10% by weight, and 20% by eight respectively of polyethylene;
FIG. 7 is a plan view illustrating one embodiment of a slide fastener made of a synthetic resin;
FIG. 8 is a plan view illustrating another embodiment of a slide fastener made of a synthetic resin;
FIG. 9 is a plan view illustrating still another embodiment of a slide fastener made of a synthetic resin; and
FIG. 10 is a partially cutaway plan view illustrating another embodiment of a slide fastener made of a synthetic resin.